This invention reaates to a method for preparing hexabromocyclododecane.
Hexabromocyclododecane has been widely used as a flame retardant for molded or foamed thermoplastic products such as those made of polyolefin or polystyrene. It also finds use in the fireproofing treatment of textile products in the form of a latex or water-suspension.
Hexabromocyclododecane may be synthesized by brominating 1,5,9-cyclododecatriene. It is desirable for the resulting product to be colorless and free of low melting point by-products as far as possible, particularly when it is intended to use with high impact strength polystyrene resins comprising polyolefin, polystyrene and styrene-butadiene copolymer.
In the conventional process, the bromination of 1,5,9-cyclododecatriene is carried out in a solvent such as ethanol. The mother liquor from which crystals of the resulting hexabromocyclododecane are separated is reused in the next bromination reaction.
This known process, however, suffers from certain disadvantages in that the product is contaminated with significant amounts of low melting point by-products. Further purification requires washing the raw product with a large amount of solvent such as clean ethanol one or several times. This, of course, increases cost while decreasing the yield of pure product.